U.S. patent number 9,135,933 [Application Number 14/075,710] was granted by the patent office on 2015-09-15 for tapered write head for mamr.
This patent grant is currently assigned to HGST NETHERLANDS B.V.. The grantee listed for this patent is HGST Netherlands B.V.. Invention is credited to Isao Nunokawa, Mikito Sugiyama, Yuta Udo.
United States Patent |
9,135,933 |
Nunokawa , et al. |
September 15, 2015 |
Tapered write head for MAMR
Abstract
Embodiments described herein provide an MAMR head structure
which provides a magnetic recording device equipped with a high
density recording magnetic head. Characteristic variations caused
by misalignment of a main pole and a STO may be reduced because the
STO may be aligned with a position on the main pole where the field
intensity is enhanced. The enhanced field intensity may be provided
by an angle of inclination .theta.1 of an inclined surface on which
the STO may be formed when compared to an angle of inclination
.theta.2 around the main pole in the region of the ABS. Further
embodiments provide a method for producing an MAMR head in which an
exposed surface of the main pole has an angle of inclination
.theta.2 which is less than the angle of inclination .theta.1 for
the inclined surface of the main pole where the STO is mounted.
Inventors: |
Nunokawa; Isao (Odawara,
JP), Sugiyama; Mikito (Odawara, JP), Udo;
Yuta (Odawara, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
HGST Netherlands B.V. |
Amsterdam |
N/A |
NL |
|
|
Assignee: |
HGST NETHERLANDS B.V.
(Amsterdam, NL)
|
Family
ID: |
53043603 |
Appl.
No.: |
14/075,710 |
Filed: |
November 8, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150131184 A1 |
May 14, 2015 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B
5/3116 (20130101); G11B 5/1278 (20130101); G11B
5/3146 (20130101); G11B 5/3163 (20130101); G11B
5/332 (20130101); G11B 5/35 (20130101); G11B
2005/0024 (20130101) |
Current International
Class: |
G11B
5/17 (20060101); G11B 5/35 (20060101); G11B
5/00 (20060101); G11B 5/33 (20060101); G11B
5/31 (20060101); G11B 5/127 (20060101) |
Field of
Search: |
;360/125.3,125.31,125.71,128 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Guan et al.;"A Trailing Shield Perpendicular Writer Design With
Tapered Write Gap for High Density Recording"; IEEE Transactions on
Magnetics, vol. 44, No. 11, Nov. 2008; 4 pages. cited by
applicant.
|
Primary Examiner: Polo; Gustavo
Attorney, Agent or Firm: Patterson & Sheridan, LLP
Claims
What is claimed is:
1. A MAMR head, comprising: a main pole, wherein a first region of
the main pole has an angle of inclination .theta.1 and a second
region of the main pole has an angle of inclination .theta.2 which
is different from the angle of inclination .theta.1; a trailing
shield formed on a trailing side of the main pole; and an STO
formed on the main pole adjacent an ABS, wherein the STO is formed
on the first region of the main pole, wherein a width of the first
region of the main pole adjacent the ABS is substantially identical
to a width of the STO, wherein the width of the first region of the
main pole remains constant extending away from the ABS, wherein a
width of the second region of the main pole expands extending away
from the ABS.
2. The MAMR head of claim 1, wherein the angle of inclination
.theta.1 and the angle of inclination .theta.2 satisfy the
relationship .theta.1>.theta.2.
3. The MAMR head of claim 2, wherein the angle of inclination
.theta.1 is between about 20.degree. and about 30.degree..
4. The MAMR head of claim 3, wherein the angle of inclination
.theta.2 is between about 10.degree. and about 20.degree..
5. The MAMR head of claim 1, wherein the trailing shield, the first
region of the main pole, and the second region of the main pole
comprise a beveled edge.
6. A MAMR head, comprising: a main pole, wherein a first region of
the main pole has an angle of inclination .theta.1 and a second
region of the main pole has an angle of inclination .theta.2,
wherein the angle of inclination .theta.1 and the angle of
inclination .theta.2 satisfy the relationship .theta.1>.theta.2;
a trailing shield formed on a trailing side of the main pole; and
an STO formed on the first region of the main pole adjacent an ABS,
wherein the STO defines a width of the first region of the main
pole at the ABS, wherein the width of the first region of the main
pole expands to form a trapezoidal shape extending away from the
ABS.
7. The MAMR head of claim 6, wherein the angle of inclination
.theta.1 is between about 20.degree. and about 30.degree..
8. The MAMR head of claim 7, wherein the angle of inclination
.theta.2 is between about 10.degree. and about 20.degree..
9. The MAMR head of claim 6, wherein a width of the second region
of the main pole is reduced extending away from the ABS.
10. The MAMR head of claim 6, wherein the trailing shield, the
first region of the main pole, and the second region of the main
pole comprise a beveled edge.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiments described herein generally relate to a magnetic
recording device for recording/reproducing data using the
magnetization state of a recording medium. More specifically,
embodiments described herein relate to a tapered write head for
microwave assisted magnetic recording (MAMR).
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically
includes a rotating magnetic disk, a slider that has read and write
heads, a suspension arm above the rotating disk and an actuator arm
that swings the suspension arm to place the read and/or write heads
over selected circular tracks on the rotating disk. The suspension
arm biases the slider into contact with the surface of the disk
when the disk is not rotating but, when the disk rotates, air is
swirled by the rotating disk adjacent an air bearing surface (ABS)
of the slider causing the slider to ride on an air bearing a slight
distance from the surface of the rotating disk. When the slider
rides on the air bearing, the write and read heads are employed for
writing magnetic impressions to and reading magnetic signal fields
from the rotating disk. The read and write heads are connected to
processing circuitry that operates according to a computer program
to implement the writing and reading functions.
In recent years, the data recording density of magnetic recording
devices has continued to increase and the size of 1 bit of a
magnetic recording mark for recording to a magnetic medium
continues to become smaller. When the magnetic recording density
exceeds about 1 Tera bit per square inch (Tbpsi), there is a risk
of data recorded to a magnetic recording medium being erased at
room temperature due to the effects of heat fluctuation. In order
to prevent data from being erased by the effect of heat
fluctuation, it is generally necessary to raise the coercive force
of the magnetic recording medium. However, there is a limit to the
amount of magnetic flux released by a magnetic recording head from
recording data by magnetization reversal of a magnetic recording
medium.
Measures for solving the above referenced problem have recently
focused on assisted recording systems for recording data in
conjunction with other technology. One such measure that has been
proposed to achieve a high recording density is a method in which a
MAMR head is utilized. A high frequency magnetic field is applied
to recording bits in a magnetic recording medium in order to weaken
the coercive force of the recording bits. In this method, data may
be recorded using a conventional magnetic recording head. A MAMR
enabled magnetic recording head utilizes a spin torque oscillator
(STO) for generating a microwave (high frequency AC magnetic
field). Typically the STO may include a field generation layer
(FGL) for generating an AC magnetic field, a spacer layer, and a
spin polarization layer (SPL) for transmitting spin polarized
torque. When the magnetic field from the write head is applied and
current is conducted to the STO, the STO oscillates and may provide
an AC magnetic field to the medium. The AC magnetic field may
reduce the coercive force of the recording medium, thus high
quality recording by MAMR may be achieved.
A MAMR head provides an effective assistance effect that enables a
high recording density by virtue of the fact that an oscillator for
generating a high frequency magnetic field is provided at a
position of a main pole where the field intensity and magnetic
field gradient are highest in the region of the ABS. In order to
write data to the magnetic recording medium, in conjunction with
the main pole of the magnetic head, the magnetic field may be
concentrated on the magnetic recording medium. However, the main
pole and the oscillator which are formed in different production
processes are likely to have characteristic variations due to
misalignment. The misalignment may reduce reliability of the MAMR
head.
Therefore, there is a need in the art for an apparatus having a
properly aligned main pole and oscillator in an MAMR head. Further,
there is a need in the art for methods of forming an aligned main
pole and oscillator in an MAMR head.
SUMMARY OF THE INVENTION
Embodiments described herein provide an MAMR head structure which
provides a magnetic recording device equipped with a high density
recording magnetic head. Characteristic variations caused by
misalignment of a main pole and a STO may be reduced because the
STO may be aligned with a position on the main pole where the field
intensity is enhanced. The enhanced field intensity may be provided
by an angle of inclination .theta.1 of an inclined surface on which
the STO may be formed when compared to an angle of inclination
.theta.2 around the main pole in the region of the ABS. Further
embodiments provide a method for producing an MAMR head in which an
exposed surface of the main pole has an angle of inclination
.theta.2 which is less than the angle of inclination .theta.1 for
the inclined surface of the main pole where the STO is mounted.
In one embodiment, an MAMR head is provided. The MAMR head may
comprise a main pole, a trailing shield formed on a trailing side
of the main pole, and an STO formed on the main pole adjacent an
ABS. A first region of the main pole may have an angle of
inclination .theta.1 and a second region of the main pole may have
an angle of inclination .theta.2 which is different from the angle
of inclination .theta.1.
In another embodiment, an MAMR head is provided. The MAMR head may
comprise a main pole, a trailing shield formed on a trailing side
of the main pole, and an STO formed on the main pole adjacent an
ABS. A first region of the main pole may have an angle of
inclination .theta.1 and a second region of the main pole may have
an angle of inclination .theta.2. The angle of inclination .theta.1
and the angle of inclination .theta.2 may satisfy the relationship
.theta.1>.theta.2.
In yet another embodiment, a method of forming an MAMR head is
provided. The method may comprise providing an MAMR substrate
comprising a main pole and a trailing shield. A layered film may be
formed over the MAMR substrate. The layered film may be masked with
a processing mask. The layered film may be etched to expose a first
region of the main pole and the main pole may be further etched to
expose a second region of the main pole.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the
present invention can be understood in detail, a more particular
description of the invention, briefly summarized above, may be had
by reference to embodiments, some of which are illustrated in the
appended drawings. It is to be noted, however, that the appended
drawings illustrate only typical embodiments of this invention and
are therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
FIG. 1 illustrates an exemplary magnetic disk drive, according to
certain embodiments.
FIG. 2 is a cross-sectional side view of a read/write head and
magnetic disk of the disk drive of FIG. 1, according to certain
embodiments.
FIG. 3 is a schematic, cross-sectional view of a portion of an MAMR
head according to one embodiment.
FIG. 4A is a schematic, perspective view of a conventional MAMR
head.
FIG. 4B is a schematic, cross-sectional side view of the MAMR head
of FIG. 4A.
FIG. 5A is a schematic, perspective view of an MAMR head according
to one embodiment.
FIG. 5B is a schematic, cross-sectional side view of the MAMR head
of FIG. 5A.
FIGS. 6A and 6C are schematic, perspective views of an MAMR head
according to various embodiments.
FIGS. 6B and 6D are schematic, cross-sectional side views of the
MAMR heads of FIGS. 6A and 6C, respectively.
FIGS. 7A-7D are schematic, bottom views of an MAMR head at the ABS
according to one embodiment.
FIG. 8 graphically depicts the results of three dimensional
magnetic field calculations of the field intensity distribution in
the tack width direction using the examples of FIGS. 7A-7D.
FIG. 9 depicts a flowchart showing a method of forming an MAMR head
according to one embodiment.
To facilitate understanding, identical reference numerals have been
used, where possible, to designate identical elements that are
common to the figures. It is contemplated that elements disclosed
in one embodiment may be beneficially utilized on other embodiments
without specific recitation.
DETAILED DESCRIPTION
In the following, reference is made to embodiments of the
invention. However, it should be understood that the invention is
not limited to specific described embodiments. Instead, any
combination of the following features and elements, whether related
to different embodiments or not, is contemplated to implement and
practice the invention. Furthermore, although embodiments of the
invention may achieve advantages over other possible solutions
and/or over the prior art, whether or not a particular advantage is
achieved by a given embodiment is not limiting of the invention.
Thus, the following aspects, features, embodiments and advantages
are merely illustrative and are not considered elements or
limitations of the appended claims except where explicitly recited
in a claim(s). Likewise, reference to "the invention" shall not be
construed as a generalization of any inventive subject matter
disclosed herein and shall not be considered to be an element or
limitation of the appended claims except where explicitly recited
in a claim(s).
The MAMR head structure, according to various embodiments described
herein, provides a magnetic recording device equipped with a high
density recording magnetic head in which characteristic variations
caused by misalignment of the main pole and STO are restricted
because the STO is aligned with a position on the main pole where
the field intensity is enhanced. The positioning of the STO may
result from increasing the angle of inclination of the surface on
which the STO is provided as compared to the angle of inclination
around the main pole in the region of the ABS. Data may be
prevented from being erased do to the effect of heat fluctuation as
a result of the high frequency magnetic field of the STO and the
magnetic flux of the main pole being concentrated and irradiated
onto the magnetic recording medium. Thus, data may be recorded to
the magnetic recording medium which exhibits an increased coercive
force.
A method for producing an MAMR head, according to various
embodiments described herein, provides a head in which the inclined
surface on the trailing side of the main has an angle of
inclination which is lower than the angle of inclination where the
STO is provided.
FIG. 1 illustrates a top view of an exemplary hard disk drive (HDD)
100. The HDD 100 may include one or more magnetic disks 110, an
actuator 120, actuator arms 130 associated with each of the
magnetic disks 110, and a spindle motor 140 affixed in a chassis
150. The one or more magnetic disks 110 may be arranged vertically
as illustrated in FIG. 1. Moreover, the one or more magnetic disks
may be coupled with the spindle motor 140.
The magnetic disks 110 may include circular tracks of data on both
the top and bottom surfaces of the disk. A magnetic head 180
mounted on a slider may be positioned adjacent a track. As each
disk spins, data may be written on and/or read from the data track.
The magnetic head 180 may be coupled to the actuator arm 130. The
actuator arm 130 may be configured to swivel around an actuator
axis 131 to place the magnetic head 180 adjacent a particular data
track.
The above description of a typical magnetic disk storage system and
the accompanying illustration of FIG. 1 are for representation
purposes only. It should be apparent that disk storage systems may
contain a large number of disks and actuators, and each actuator
may support a number of sliders.
FIG. 2 is a fragmented, cross sectional side view through the
center of a MAMR read/write head 200 facing a magnetic disk 202.
The read/write head 200 and the magnetic disk 202 may correspond to
the magnetic head assembly 180 and the magnetic disk 110,
respectively in FIG. 1. The read/write head 200 may include an ABS,
a magnetic write head 210 and a magnetic read head 211, and may be
mounted such that the ABS faces the magnetic disk 202. In FIG. 2,
the disk 202 moves past the write head 210 in the direction
indicated by the arrow 232.
The magnetic read head 211 may be a magnetoresistive (MR) read head
that includes an MR sensing element 204 located between MR shields
S1 and S2. In other embodiments, the magnetic read head 211 may be
a magnetic tunnel junction (MTJ) read head that includes an MTJ
sensing device 204 located between MR shields S1 and S2. The
magnetic fields of the adjacent magnetized regions in the magnetic
disk 202 are detectable by the MR (or MTJ) sensing element 204 as
the recorded bits.
The write head 210 may include a return pole 206, a spin torque
oscillator (STO) 230 disposed between a main pole 220 and a
trailing shield 240, and a coil 218 that excites the main pole 220.
A recording magnetic field generated from the main pole 220 and the
trailing shield 240 helps making the magnetic field gradient of the
main pole 220 steep. The main pole 220 may be a magnetic material
such as a CoFe alloy. In one embodiment, the main pole 220 may have
a saturated magnetization (Ms) of 2.4 T and a thickness of about
300 nanometers (nm). The trailing shield 240 may be a magnetic
material such as NiFe alloy. In one embodiment, the trailing shield
240 has an Ms of about 1.2 T.
The main pole 220 and the trailing shield 240 have ends 260, 270
defining part of the ABS, and the STO 230 may be disposed between
the main pole 220 and the trailing shield 240. The STO 230 may be
surrounded by an insulating material in a cross-track direction
(into and out of the paper). During operation, the STO 230
generates an AC magnetic field that travels to the magnetic disk
202 to lower the coercivity of the region of the magnetic disk 202
adjacent to the STO 230. The STO 230 will be discussed in detail
below. The write head 210 may also include a heater 250 for
adjusting the distance between the read/write head 200 and the
magnetic disk 202. The location of the heater 250 is not limited to
above the return pole 206, as shown in FIG. 2. The heater 250 may
be disposed at any suitable location.
FIG. 3 is a schematic, cross-sectional view of a portion of an MAMR
head 300. The MAMR head 300 may comprise a main pole 302, an STO
304 for generating a high frequency magnetic field, and a trailing
shield 306. The STO 304 may be disposed on an inclined surface 308
on a trailing side 312 of the main pole 302 between the main pole
302 and the trailing shield 306. A bias current for exciting a high
frequency magnetic field may flow by way of the main pole 302 and
the trailing shield 306.
The STO 304 may have a layered structure comprising a perpendicular
magnetic anisotropic body, a magnetization high speed rotating
body, a nonmagnetic metal spin conduction layer, and a spin
injection layer. The perpendicular magnetic anisotropic body may
comprise materials such as hexagonal-crystal CoCrPt, NiCo, or the
like. The magnetization high speed rotating body may comprise a
material such as a CoFe allow or the like and may have a thickness
having a high level of saturation magnetization and substantially
no crystal magnetic anisotropy. The thickness of the magnetization
high speed rotating body may be between about 0.010 .mu.m and about
0.020 .mu.m. The nonmagnetic metal spin conduction layer may
comprise a material such a Ru or Cu, which exhibit high spin
conductivity and the spin injection layer may comprise a material
such as CoPt or the like.
In operation, when the STO 304 applies a bias current for exciting
a high frequency magnetic field between the main pole 302 and the
trailing shield 306, the magnetization rotates at a high speed
within a plane along the layer of the magnetization high speed
rotating body. A leakage magnetic field from an ABS may be locally
irradiated onto a magnetic recording medium as a high frequency
magnetic field.
The main pole 302 may have an inverse trapezoidal shape which may
be provided with a bevel for preventing erasure of adjacent track
data when the MAMR head 300 moved over the magnetic recording
medium. The STO 304 may be disposed in a region of a track center
of the main pole 302 in order to locally concentrate the magnetic
flux emitted by the main pole 302 and the high frequency magnetic
field emitted by the STO 304. As previously discussed, the main
pole may have an inclined surface 308 which may increase in
thickness in the element height direction on the trailing side 312
and leading side 314. When the inclined surface 308 is provided,
the magnetic flux of the induction field excited by a coil is
inducted in a concentrated manner to the ABS. Thus, the intensity
of the magnetic field emitted onto the magnetic recording medium
may be enhanced.
It is believed that the amount of magnetic flux emitted by the main
pole 302 and the magnetic field distribution in the track direction
fluctuates because of the angle of inclination of the inclined
surface 308. Thus, the STO 304 may be provided on the trailing side
312 of the main pole 302 where the field intensity distribution is
stable to produce stable oscillation characteristics.
FIG. 4A is a schematic, perspective view of a conventional MAMR
head 400. The MAMR head 400 may comprise a main pole 402, a
trailing shield 406, and a side gap 410 disposed between the main
pole 402 and the trailing shield 406. An STO 404 may be mounted on
a trailing side 412 of the main pole 402 near the ABS. In this
example, a width of the main pole 402 may be reduced such that the
width narrows from the element height direction toward the ABS. The
angle at which the main pole 402 narrows may be about
45.degree..
FIG. 4B is a schematic, cross-sectional side view of the MAMR head
400 of FIG. 4A. An inclined surface 408 may be formed on the main
pole 402 having an angle of inclination .theta.1 on the trailing
side 412 of the main pole 402 to intensify the magnetic field. A
thickness of the main pole 402 may define the shape of the main
pole 402 at the ABS. The STO 404 may be mounted on the inclined
surface 408 of the trailing side 412 of the main pole 402.
In general, several thousand to tens of thousands of elements are
produced in a single substrate when the STO 404 is mounted on the
main pole 402. Thus, the STO 404 may be misaligned on the main pole
402 due to variations within the plane of the substrate. As a
result of misalignment, the mounting position of the STO 404 may be
offset from a position on the main pole 402 facing the magnetic
recording medium where there is an intense magnetic field from the
magnetic flux emission surface and stable field distribution. If a
stable assistance effect cannot adequately be provided, there may
be characteristic variations in the MAMR head 400 and the recording
characteristics may be affected.
FIG. 5A is a schematic, perspective view of an MAMR head 500
according to one embodiment. FIG. 5B is a schematic,
cross-sectional side view of the MAMR head of FIG. 5A. Elements of
the MAMR head 500 which are the same as the elements of MAMR head
400 of FIGS. 4A-4B will not be discussed for the sake of brevity.
The STO 404 and main pole 402 may comprise a layered film and may
be formed using a processing pattern in which a width of the STO
404 is processed on an inclined surface 408 having an angle of
inclination .theta.1 which is provided on the trailing side 412 of
the main pole 402. The angle of inclination .theta.1 may be
determined from a datum plane reference which is shown as a
horizontal dotted line in FIG. 5B. The inclined surface 408 may
maintain substantially the same width as the STO 404 about 150 nm
or less from the ABS extending to the trailing side 412.
A second inclined surface 502 having an angle of inclination
.theta.2, depicted by the dotted line in FIG. 5B, may be formed on
the exposed surface 504 of the main pole 402. The second inclined
surface may be recessed from the first inclined surface by a
distance of between about 10 nm and about 15 nm, for example, when
the angle of inclination .theta.1 is between about 24.degree. and
about 26.degree. and the angle of inclination .theta.2 is between
about 20.degree. and about 22.degree.. Similar to the angle of
inclination .theta.1, the angle of inclination .theta.2 may be
determined from the datum plane reference. The exposed surface 504
may be formed on either side of the STO 404 on the main pole 402.
The exposed surface 504 may expand laterally outward to increase a
width of the exposed surface 504 from the ABS toward the trailing
side 412 over a certain length. For example, a width of the exposed
surface 504 at its largest may be slightly greater than a distance
formed by the masked portion of the STO 504 extending from a
termination edge of the ABS into the main pole 402. A portion of
the main pole 402 having a width similar to the width of the STO
404 at the ABS may not be exposed. The STO 404 may be mounted on
the main pole 402 which may be processed to the height of the STO
404 from the ABS. The trailing side 412 inclined surface of the
main pole 402 may comprise the first inclined surface 408 having an
angle in inclination .theta.1 and the second inclined surface
having an angle of inclination .theta.2. A relationship between the
angles of inclination may be .theta.1>.theta.2.
If .theta.1=.theta.2, misalignment (described with regard to FIGS.
4A-4B) may be problem. Further, if .theta.1=.theta.2 and the ABS of
the main pole 402 is processed to a convex state in order to
produce the same effect as when .theta.1>.theta.2, the ABS
surface area of the main pole 402 is reduced. The amount of
magnetic flux is limited in accordance with the ABS surface area
and reducing the ABS surface are of the main pole 402 in order to
vary the field distribution of the inclined surface 408 of the main
pole 402 where the STO 404 is provided reduces the write field
intensity emitted by the main pole 402. The reduction in intensity
causes magnetization reversal of the magnetic recording medium.
When .theta.1>.theta.2, a magnetic body on the trailing side 412
of the main pole 402 in the height direction of the STO 404 from
the ABS may be processed to reduce the angle of inclination. The
second inclined surface having an angle of inclination .theta.2 may
restrict the amount of magnetic flux supplied on either side of the
STO 404. In this example, the main pole 404 ABS surface area is not
reduced and it is possible to obtain a high field intensity and a
stable field distribution. Even if the main pole 402 and the STO
404 are misaligned, a high field intensity may be realized where
the STO 404 is mounted.
FIG. 6A is a schematic, perspective view of an MAMR head 600
according to certain embodiments. FIG. 6B is a schematic,
cross-sectional side view of the MAMR head 600 of FIG. 6A. The MAMR
head 600 of FIGS. 6A-6B may be similar to the MAMR head 500 of
FIGS. 5A-5B. However, an expanded portion 602 of the main pole 402
may be defined by the width of the STO 404 at the ABS and may
expand in the shape of a trapezium to form an upper edge 604. The
upper edge 604 may be substantially the same height as a height of
the STO 404. The expanded portion 602 may reduce the exposed
surface 502 of the main pole 402. In one example, the expanded
portion 602 may expand at an angle of about 45.degree. from a
centerline extending from the ABS through the STO 404 to the main
pole 402. An amount of the exposed surface 502 in FIG. 6A when
compared to the exposed surface 502 in FIG. 5A may be about 25%
less due to the expanded portion 602. If the angle of inclination
.theta.1 of the inclined surface 408 of the main pole 402 upon
which the STO 404 is mounted is such that .theta.1>.theta.2, the
MAMR head 600 may produce a high field intensity and stable field
distribution even if the main pole 402 and STO 404 are
misaligned.
FIG. 6C is a schematic, perspective view of an MAMR head 650
according to certain embodiments. FIG. 6D is a schematic,
cross-sectional side view of the MAMR head 650 of FIG. 6C. The MAMR
head 650 of FIGS. 6C-6D may be similar to the MAMR head 600 of
FIGS. 6A-6B, however a non-magnetic layer 607 is disposed over the
main pole 402. The non-magnetic layer 607 may be laminated at the
trailing side 412 of the main pole 402 and may comprise materials
such as NiCr or Al.sub.2O.sub.3. The first inclined surface 408 may
extend vertically from the ABS to the main pole 402, the first
inclined surface 408 being extended by a sloped surface 606 of the
non-magnetic layer 607 to form a planar surface 605. In one
example, the main pole 402 exposed adjacent the first inclined
surface 408 is reduced by the presence of the sloped surface 606 of
the non-magnetic layer 607. The first angle of inclination .theta.1
defined by the sloped surface 606 may be greater than the second
angle of inclination .theta.2 defined by exposed portions of the
main pole 402. Although magnetic flux may be absorbed by the
trailing shield 406, it is possible to acquire the same advantages
with the non-magnetic layer 607 as the MAMR head 600 of FIGS.
6A-6B.
FIGS. 7A-7D are schematic, bottom views of an MAMR head at the ABS.
In FIGS. 7A-7D, an STO is not shown for the sake of clarity. FIG.
7A may correlate to the MAMR head 400 of FIGS. 4A-4B. FIG. 7B may
correlate to the MAMR head 500 of FIGS. 5A-5B and FIGS. 7C-7D may
correlate to the MAMR head 600 of FIGS. 6A-6B. FIG. 7A depicts a
portion of the main pole 402 wherein the inclined surface 408 has
an angle of inclination .theta.1=25.degree.. Thus, the inclined
surface 408 of the main pole 402 is tapered at an angle of
25.degree. away from the ABS. In this example, the main pole 402 is
not etched to lower the element height of the main pole 402.
FIG. 7B depicts a portion of the main pole 402 wherein the inclined
surface 408 may taper at an angle of inclination .theta.1=between
about 20.degree. and about 30.degree., such as about 25.degree. and
the exposed surface 502 of the main pole 402 may be removed and
taper at an angle of inclination .theta.2=between about 10.degree.
and about 20.degree., such as about 15.degree.. Thus, the inclined
surface 408 and the exposed surface 502 may not occupy a single
plane because the angles of inclination are different. A width of
the inclined surface 408 may correlate to a width of an STO (not
shown) mounted on the main pole 402 at the ABS.
FIG. 7C depicts a portion of the main pole 402 wherein the inclined
surface 408 may taper at an angle of inclination .theta.1=between
about 20.degree. and about 30.degree., such as about 25.degree. and
the expanded portion 602 of the main pole 402 may be removed and
taper at an angle of inclination .theta.2=between about 10.degree.
and about 20.degree., such as about 15.degree.. Thus, the inclined
surface 408 and the expanded portion 602 may not occupy a single
plane because the angles of inclination are different. The first
inclined surface 408 may comprise a trapezoidal shape where a width
of the STO (not shown) may define a width of the inclined surface
408 at ABS and may expand by an angle of between about 10.degree.
and about 20.degree., such as about 15.degree. away from the
ABS.
FIG. 7D depicts a portion of the main pole 402 wherein the inclined
surface 408 may taper at an angle of inclination .theta.1=between
about 20.degree. and about 30.degree., such as about 25.degree. and
the expanded portion 602 of the main pole 402 may be removed and
taper at an angle of inclination .theta.2=between about 10.degree.
and about 20.degree., such as about 15.degree.. Thus, the inclined
surface 408 and the expanded portion 602 may not occupy a single
plane because the angles of inclination are different. The first
inclined surface 408 may comprise a trapezoidal shape where a width
of the STO (not shown) may define a width of the inclined surface
408 at ABS and may expand by an angle of between about 10.degree.
and about 20.degree., such as about 30.degree. away from the
ABS.
FIG. 8 graphically depicts the results of three dimensional
magnetic field calculations of the field intensity distribution in
the tack width direction using the examples of FIGS. 7A-7D. Model 1
corresponds to FIG. 7A, model 2 corresponds to FIG. 7B, Model 3
corresponds to FIG. 7C, and model 4 corresponds to FIG. 7D. The
calculation conditions are described below. The vertical axis shows
the field intensity obtained from the three dimensional magnetic
field calculation results while the horizontal axis shows the
position in the track width direction on one side from the center
of the main pole.
The main pole was covered by a magnetic shield with an interposed
nonmagnetic layer. The shield material was assumed to be 80 at %
Ni, and 20 at % Fe having a saturation magnetic flux density of 1.0
T. The gap between the main pole and the trailing side shield was
0.020 .mu.m. The gap between the main pole and the width direction
shield was 0.080 .mu.m. The gap between the main pole and the
leading side shield was 0.120 .mu.m. The main pole had the shape of
an inverse trapezium having a trailing side width of 0.050 .mu.m
and a bevel angle of 11.degree.. The material was assumed to be
CoNiFe with a saturation magnetic flux density of 2.4 T and
relative permeability of 500.
For the field intensity measurement, the value at the center
position of the recording layer of the magnetic recording medium
was calculated. The magnetic recording medium used for the
calculations was a material for a soft magnetic backing layer
having a saturation magnetic flux density of 1.1 T. The thickness
of the magnetic recording layer was assumed to be 0.019 .mu.m and
the thickness of the interlayer was assumed to be 0.020 .mu.m. The
flying amount of the head slides was taken as 0.011 .mu.m, and the
distance of the magnetic recording layer to the measurement
position was 0.0205 .mu.m.
In contrast to Model 1 (a conventional example), Models 3 and 4 may
have the same field intensity distribution up to the region of 20
nm in the track width direction on one side of the main pole. The
field intensity of Models 3 and 4 are lower than in Model 1 due to
the effect of restricting the supply of magnetic flux which is a
result of reducing the angle of inclination of the inclined surface
from 25.degree. to 15.degree. away from the track center. For
example, if the field intensity of the main pole which is required
to record data to the magnetic recording medium is assumed to be at
least 11 kOe, 84 nm track data is written in Model 1 when the
position in the track width direction on one side from the center
is roughly equal to 42 nm and the write spread is roughly equal to
17 nm with respect to a track width of 25 nm on one side of the
main pole. In Models 3 and 4, 76 nm track data is written for a
position of roughly 38 nm and the write spread at roughly 8 nm per
track is suppresses with respect to Model 1.
In Model 2, the surface of the main pole with an angle of
inclination .theta.2 provides a reduction in the amount of magnetic
flux applied and the field intensity drops by about 0.2 kOe with
respect to Model 1. If the angle of inclination is set in such a
manner that .theta.1>.theta.2, write spread in the track width
direction may be suppressed in the same way as Models 3 and 4. By
forming the main pole such that the angles of the inclined surfaces
on the trailing side of the main pole satisfies
.theta.1>.theta.2, it is possible to shorten the distance
between tracks. The assistance effect for locally concentrating the
high frequency magnetic field and the main pole magnetic flux may
maintain an adequate field intensity even if the STO is misaligned.
As a result, a higher recording density may be achieved.
FIG. 9 depicts a method 900 of forming an MAMR head. In the method
900 described below, the MAMR head, when completely processed, may
be substantially similar to the MAMR head 600 of FIGS. 6A-6B. The
method 900 may also be utilized to form the MAMR head 500 of FIGS.
5A-5B. The method at operation 905 provides a MAMR head substrate
which may comprise the main pole and the trailing shield. The
trailing shield may be formed on either side of the main pole. The
side gap, which may be a nonmagnetic layer, may be interposed
between the main pole and the trailing shield. The main pole may
comprise an inverse trapezoidal shape in which the trailing side
width may increase and a bevel angle may be provided on the
trailing side surface. The trailing side surface may have a flared
shape which may expand in the element height direction. The main
pole may be formed from a magnetic material, such as CoNiFe, having
a saturation magnetic flux density of 2.4 T. The main pole may be
formed by a process, such as plating, and then may be planarized by
a process such as chemical mechanical polishing (CMP). After
planarization, a processing mask, such as a photosensitive resist
material, may be provided in the element height direction to form
the inclined surface having an angle of inclination .theta.1 from
the ABS. The inclined surface may be formed or etched by an ion
milling process or the like and the processing mask may then be
removed.
At operation 910, a layered film may be formed over the entire MAMR
head substrate. The layered film may comprise a perpendicular
magnetic anisotropic body, a magnetization high speed rotating
body, a nonmagnetic metal spin conduction layer, and a spin
injection layer. The layered film may form the STO upon further
processing. The layered film may be deposited by a multiple source
sputtering apparatus or the like. At operation 915, a processing
pattern may be provided over the layered film. The processing
patter may determine the width of the STO and may have a trapezium
shape. The processing pattern may be similar to the processing mask
described above in operation 905.
At operation 920, the layered film may be etched by an ion milling
process of the like in the pattern of the processing pattern. The
layered film may be etched to expose a portion of the main pole.
The exposed portion of the main pole may be a magnetic film. The
amount of etching performed on the layered film may be determined
by monitoring the elements in the layered film until a desired end
point is reached.
At operation 925, an etching operation may be performed on the
exposed magnetic film on the trailing side of the main pole. The
etching may be performed using the same processes used to etch the
layered film. As such, an ion beam incident angle and incident
range may be regulated in order to form the inclined surface angle
.theta.2 on the exposed magnetic film of the main pole. At this
point, the layered film has formed the STO and the STO may be
electrically insulated to allow for the flow of a bias current
which excited a high frequency magnetic field by way of the main
pole and the trailing shield. An oxide film, such as aluminum
oxide, may be used as the insulating material. At operation 930,
the aluminum oxide film may be formed over the entire surface of
the MAMR head substrate while the processing mask remains in place.
At operation 935, the processing mask may be processed using CMP or
the like to expose an upper surface of the processing mask. Further
at operation 935, the processing mask and excess aluminum oxide
film may be removed using a lift-off process or the like by
employing a chemical solution, such as an anisotropic etchant. The
resulting STO may be electrically insulated in the width
direction.
After operation 935, the trailing side of the main pole on the
inclined surface may have an angle of inclination .theta.1 while
the layered film covers a portion of the main pole. The angle of
inclination .theta.2 of the magnetic film of the main pole and the
angle of inclination .theta.1 may satisfy a relationship such that
.theta.1>.theta.2.
At operation 940, a height of the STO may be determined. The
layered film may be etched by ion milling or the like to form a
desired STO height. At operation 945, an insulator, such as
aluminum oxide or the like, may be formed over the etched layered
film (STO) to provide electrical insulation. At operation 950, the
insulator may be removed by a lift-off process of the like, to form
insulation on the STO in the height direction.
In the resulting MAMR head, the STO for generating a high frequency
magnetic field is mounted on the inclined surface of the main pole.
The trailing shield may serve as an electrode to enable a flow of
bias current to excite a high frequency magnetic field. The
inclined surface of the main pole having the angle of inclination
.theta.1 may provide a desirable field intensity and field
distribution. A state of magnetic alignment may be achieved such
that the high frequency magnetic field generated by the oscillator
and the magnetic flux of the main pole are locally concentrated on
the magnetic recording medium which is positioned in operation
opposite the STO.
It is also contemplated that the embodiments described above may be
employed when the ABS of the main pole is recessed. If the ABS is
recessed, the same effects may still be achieved provided that the
relationship between the angle of inclination .theta.1 of the
inclined surface of the main pole and the exposed magnetic film
having an angle of inclination .theta.2 satisfy the relationship
.theta.1>.theta.2. In this embodiment, the amount of tapering or
recessing of the exposed magnetic film may be reduced to reduce the
amount of decrease in material in the ABS surface area.
In sum, the MAMR head structure may provide a magnetic recording
device equipped with a high density recording magnetic head.
Characteristic variations caused by misalignment of the main pole
and the STO may be reduced because the STO is aligned with a
position on the main pole where the field intensity is enhanced.
The enhanced field intensity may be provided by the angle of
inclination .theta.1 of the inclined surface on which the STO is
formed when compared to the angle of inclination .theta.2 around
the main pole in the region of the ABS. Data loss via erasure due
to the effect of heat fluctuation may be prevented because the high
frequency magnetic field of the STO and the magnetic flux of the
main pole are concentrated and irradiated onto the magnetic
recording medium. Thus, data may be recorded to the magnetic
recording medium which has an increased coercive force.
Further, the method for producing the MAMR head makes it possible
to produce a MAMR head in which the exposed surface of the main
pole has an angle of inclination .theta.2 which is less than the
angle of inclination .theta.1 for the inclined surface of the main
pole where the STO is mounted.
While the foregoing is directed to embodiments of the present
invention, other and further embodiments of the invention may be
devised without departing from the basic scope thereof, and the
scope thereof is determined by the claims that follow.
* * * * *